The present invention relates generally to an electrical connector used with an implantable medical device, such as a pacemaker, for stimulating selected body tissue for connecting an implantable electrical lead to the electrical circuits within a hermetically sealed housing of the medical device. More particularly, the present invention relates to a feedthrough connector assembly which employs shape memory alloy components for ease of manufacture and for assuring a hermetically sealed engagement with the electrical lead.
Implantable electronic devices are in use providing electronic pulses to stimulate tissue via a lead extending from an implanted pulse generator to a desired internal location. An example of this type of technology is a pacemaker and a pacing lead which provides electrical stimulation to the heart. The pacemaker is usually implanted in a subcutaneous cavity, and the leads extend either transvenously to the internal cavities of the heart, or to patch electrodes located on external surface of the heart.
The leads generally include at least one, and often two or more, electrodes located at a distal end, and a connector having a similar number of electrical connector elements for interconnection to the pulse generator at the proximal end. The electrical connector elements, or contacts, at the proximal end and the distal electrodes are interconnected by conductors extending through an insulated lead body. It is common for the leads to include helically wound conductors which are either coaxially mounted or side-by-side wound within the lead body, separated by insulation.
The connector is inserted into a receiving orifice in a header portion of the pulse generator. The header portion of the pulse generator may be formed from an epoxy material which is assembled and bonded to the main body of the pulse generator. The main body of the pulse generator is generally a metallic self-contained housing or can, which encloses the source of electrical energy and electrical circuitry for controlling the electrical stimulus delivered by the lead.
In the design of the lead connector and the pulse generator, it is important for the lead to be safely secured to the pulse generator to prevent inadvertent decoupling. Generally, connectors have been assembled using flexible insulation materials to separate the respective electrical components. Problems which arise in the construction and use of multiple conductor lead connectors are primarily related to the design of the electrical interconnection between the conductors and the contacts. The connector must be constructed in a manner which prevents fluids from invading the connector and shorting the electrical conductors therein. At the same time, simpler constructions which reduce the number of components, speed the assembly process and assure that the resulting medical device is hermetically sealed are constantly being sought.
A number of patents are representative of the prior art in this regard.
U.S. Pat. No. 4,934,366 to Truex et al. discloses a feedthrough connector for an implantable medical device which combines the connector function with the feedthrough function and eliminates the need for the cast epoxy connector previously used on such devices.
U.S. Pat. No. 5,653,759 to Hogan et al. discloses an in-vivo methodology for repairing aruptureso fragmented segment of a pre-existing therapeutic appliance which has been previously surgically positioned or implanted within a human body. The repair methodology eliminates the need for surgical excision procedures by using a guiding catheter and deformable, thermoelastic shape-memory alloy rods in order to access and repair the flawed or failing therapeutic appliance.
U.S. Pat. Nos. 5,908,447 and 5,957,966 to Schroeppel et al. both disclose a cardiac lead that includes a connector for connecting to a cardiac stimulator and a flexible sleeve coupled to the connector. The sleeve has a first segment, a second segment, and a jacket coupling the first segment and the second segment. The jacket is composed of a shape-memory polymeric material which deforms diametrically in situ to selectively disconnect the first segment from the second segment. An electrode is coupled to the sleeve and a conductor is disposed in the sleeve and coupled to the connector for conveying electrical signals. The breakaway function of the jacket allows removal of all but a small portion of the lead without dissection of fibrous tissue. It was in light of the foregoing that the present invention was conceived and has now been reduced to practice.
A feedthrough connector for an implantable medical device includes a hermetically sealed housing containing an electrical circuit and a tubular barrel with an open end and a closed end defining a tubular channel that protrudes into the sealed housing while maintaining the seal of the housing. The inside of the tubular channel is open to the outside of the sealed housing through the open end and the tubular barrel also has a plurality of circumferentially spaced openings extending between an outer peripheral surface and the tubular channel. An electrical contact assembly electrically in common with the electrical circuit within the housing serves to make electrical contact with an electrical lead axially inserted into the open end of the tubular channel. The electrical contact assembly includes a plurality of contact members received in and projecting radially through a plurality of circumferentially spaced openings and a sleeve member of shape memory alloy freely overlies the contact members when in a first deformed-shape configuration but engage the contact members and the outer peripheral surface of the tubular barrel when in a second memory-shaped configuration, urging the contact members into mechanical, electrical, and hermetically sealed engagement with the electrical lead. The tubular channel may include a plurality of conductive cylindrical portions coaxial with the axis of the tubular barrel, the dimensions of the diameter of the successive cylindrical portions progressively decreasing from the open end to the closed end.
The electrical contact assembly includes an annular spring member which overlies the plurality of circumferentially spaced openings in the tubular barrel and itself has a plurality of cicumferentially spaced holes generally aligned with the openings in the tubular barrel. The contact members are balls, each having a diameter greater than the diameter of the openings in the tubular barrel and greater than the diameter of the holes in the annular spring member. The balls are captured between the annular spring member and the tubular barrel and project through the holes for engagement with the electrical lead.
The annular spring member is discontinuous, having opposed finite ends capable of being separated against hoop bias from a closed position at which the finite ends are in a proximate relationship to an open position at which the finite ends are in a distant relationship for placement on the tubular barrel, then returned to the closed position when overlying the plurality of circumferentially spaced openings.
The tubular barrel has a pair of annular grooves in the outer peripheral surface longitudinally straddling the plurality of circumferentially spaced openings and lying in parallel spaced apart planes transverse of the tubular barrel axis. In a cooperative manner, the sleeve member has an inner peripheral surface with a pair of annular rims lying in parallel spaced apart planes aligned, respectively, with the annular grooves of the tubular barrel. With this construction, as the sleeve member assumes the second memory-shaped configuration, the annular rims of the sleeve member fittingly engage with the annular grooves of the tubular barrel and hermetically seal the region therebetween when the electrical lead is axially inserted into the open end of the tubular channel and sealingly engaged therewith.
Desirably, the tubular channel has an annular seal groove located intermediate successive cylindrical portions and includes an intermediate seal member received in the annular seal groove and engageable with the electrical lead when axially inserted into the open end of the tubular channel. In this manner, the circumferentially spaced openings associated with one cylindrical portion are isolated from the circumferentially spaced openings associated with the adjoining cylindrical portion.
In one instance, the tubular barrel is of dielectric material, ceramic for example, and includes an annular flange fixed to its open end which is welded to the housing of the implantable medical device. In this manner, the interior of the implantable medical device is hermetically sealed.
In another instance, the tubular barrel is of ceramic material and includes an integral first circular band spaced from its open end. A metallic tubular extension member is axially aligned with the tubular barrel and extends between first and second ends, the first end being proximate the tubular barrel, the tubular extension member having an annular flange at the second end, being an open end distant from the tubular barrel. The flange at the second end is welded to the housing of the implantable medical device and the tubular extension member includes an integral second circular band spaced from the first end. A connection sleeve member of shape memory alloy freely overlies the tubular barrel and the tubular extension member between the first and second circular bands when in a first deformed-shape configuration and engages the tubular barrel and the tubular extension member when in a second memory-shaped configuration to thereby firmly join the tubular barrel to the implantable medical device.
In each mentioned instance, the sleeve member assumes the first deformed-shape configuration above a predetermined temperature and assumes the second memory-shaped configuration below the predetermined temperature.
A primary feature, then, of the present invention is the provision of an improved feedthrough connector for an implantable medical device providing stimulating pulses to selected body tissue.
Another feature of the present invention is the provision of such a feedthrough connector for connecting an implantable electrical lead to the electrical circuits within a hermetically sealed housing of the medical device.
Yet another feature of the present invention is the provision of such a feedthrough connector which employs shape memory alloy components for ease of manufacture and for assuring a hermetically sealed engagement with the electrical lead.
Still another feature of the present invention is the provision of such a feedthrough connector which is assembled in a low heat sealing process using a shape memory alloy.
Yet another feature of the present invention is the provision of such a feedthrough connector which employs a reduced number of components when compared with known feedthrough connector constructions.
Still a further feature of the present invention is the provision of such a feedthrough connector using a shape memory alloy which requires only simple installation tooling, is performed at relatively low temperatures, results in a finished product which exhibits a low leakage rate, and allows sealing of dissimilar materials, such as titanium and non-methodized ceramic base.
Other and further features, advantages, and benefits of the invention will become apparent in the following description taken in conjunction with the following drawings. It is to be understood that the foregoing general description and the following detailed description are exemplary and explanatory but are not to be restrictive of the invention. The accompanying drawings which are incorporated in and constitute a part of this invention, illustrate one of the embodiments of the invention, and together with the description, serve to explain the principles of the invention in general terms. Like numerals refer to like parts throughout the disclosure.